1. Technical Field
The present invention relates to an optical photographing lens system. More particularly, the present invention relates to a compact optical photographing lens system applicable to the electronic products.
2. Description of Related Art
In recent years, with the popularity of mobile products with camera functionalities, the demand of miniaturized optical lens systems is increasing. The sensor of a conventional photographing camera is typically a CCD (Charge-Coupled Device) or a CMOS (Complementary Metal-Oxide-Semiconductor) sensor. As the advanced semiconductor manufacturing technologies have allowed the pixel size of sensors to be reduced and compact optical lens systems have gradually evolved toward the field of higher megapixels, there is an increasing demand for compact optical lens systems featuring better image quality.
Imaging lenses used in vehicle cameras, security surveillance cameras or electronic game devices typically require a larger field of view to capture an image of a larger area at one time. Generally, a conventional imaging lens assembly with a large angle of view, such as the five-element lens assembly disclosed in U.S. Pat. No. 8,248,713, is a negative-positive structure, thereby forming an inverse telephoto structure to achieve a wide field of view. While such arrangement facilitates the enlargement of the field of view, the image resolving power is insufficient and the total track of length is not easy to be reduced.
Although other conventional imaging lens assembly with six-element lens structure is favorable for improving the image resolving power, such as the one disclosed in U.S. Publication No. 2012/0188654. However, the two lens elements of the imaging lens assembly closest to the object side are not configured as the traditional one with negative refractive power and the other with greater positive refractive power, so that the back focal length of imaging lens assembly cannot be reduced. As a result, although it is favorable for reducing the total track of length, it is not favorable for enlarging the field of view to capture an image of a larger area at one time.